In a prior-art dispensing pump with pump bellows (DE 35,09,178 A1), the housing part provided with the suction valve has a cylindrical screw cap provided with internal thread which can be screwed onto the threaded neck of a bottle, can, or the like. A connection piece for a suction pipe, through which the liquid medium is drawn in from the bottle, is made in one piece with a central, cylindrical guide socket, in which the axially movable closing member of the suction valve is guided.
Aside from the fact that this dispensing pump can be screwed only onto a bottle, whose neck is provided with the fitting thread, this bottle also must be provided with a closing cover, which can be screwed off, and is removed before the dispensing pump is screwed on, and is usually discarded into the trash.
This is also true of another prior-art, manually operated dispensing pump (West German Offenlegungsschrift No. DE-OS 28,24,073), which has, in addition, too complicated a design and too large a diameter to be able to be placed on bottles with narrow necks.
Dispensing pumps of this design are suitable only for dispensing liquid media, and they must be provided with ventilating devices, through which outside air is able to enter the interior of the bottle to prevent vacuum, which would impair the pump mechanism or the pumping processes, from building up in the bottle. These prior-art dispensing pumps cannot be used and are not intended for paste-like substances, which are usually contained in paste containers with a follower plunger.
Dispensing pumps for liquid substances and/or substances of low viscosity, i.e., paste-like substances, have been known (EP-0,304,567 A1), in which a substance container of cylindrical cross section provided with a follower plunger is made in one piece with the housing part provided with the suction valve, while another embodiment can be screwed onto the threaded neck of a bottle by means of a screw cap.
No provision for refilling is made in the embodiment provided with the substance container made in one piece, because refilling would be very complicated. For refilling, the follower plunger, moved into the upper end position, would have to be destroyed and removed from the container. Therefore, these paste dispensers are used only once and are then discarded into the trash together with the dispensing pump.